Too bad gearing isn’t discussed. Just slowing down without the proper gearing may not have the desired results. It could result in constant downshifting / upshifting on anything more than an overpass. No doubt, pure physics says that slowing down will improve mpg, but when we enter the real world and don’t deal with sweet spots on engines and match them up to the proper gearing to run at those slower speeds, then general comments like saving .1 mpg for every 1 mpg slow down don’t work out as planned. And the average used truck is not spec’d properly. It almost takes spec’ing out a new truck, matched perfectly, to the speed one is wanting to operate, over the terrain they operate, with the loads they pull. Most used trucks that are spec’d right, are not on the sale lot.